selftests/landlock: UX improvements

index 73729382d40f..e65e6cc80e22 100644
@@ -5,6 +5,7 @@
  * Copyright © 2017-2020 Mickaël Salaün <[email protected]>
  * Copyright © 2020 ANSSI
  * Copyright © 2020-2022 Microsoft Corporation
+ * Copyright © 2025 Tingmao Wang <[email protected]>
  */
 
 #define _GNU_SOURCE

@@ -303,10 +304,9 @@ static void prepare_layout_opt(struct __test_metadata *const _metadata,
 	 * for tests relying on pivot_root(2) and move_mount(2).
 	 */
 	set_cap(_metadata, CAP_SYS_ADMIN);
-	ASSERT_EQ(0, unshare(CLONE_NEWNS | CLONE_NEWCGROUP));
-	ASSERT_EQ(0, mount_opt(mnt, TMP_DIR))
+	ASSERT_EQ(0, unshare(CLONE_NEWNS | CLONE_NEWCGROUP))
 	{
-		TH_LOG("Failed to mount the %s filesystem: %s", mnt->type,
+		TH_LOG("Failed to create new mount namespace: %s",
 		       strerror(errno));
 		/*
 		 * FIXTURE_TEARDOWN() is not called when FIXTURE_SETUP()

@@ -316,6 +316,12 @@ static void prepare_layout_opt(struct __test_metadata *const _metadata,
 		 */
 		remove_path(TMP_DIR);
 	}
+	ASSERT_EQ(0, mount_opt(mnt, TMP_DIR))
+	{
+		TH_LOG("Failed to mount the %s filesystem: %s", mnt->type,
+		       strerror(errno));
+		remove_path(TMP_DIR);
+	}
 	ASSERT_EQ(0, mount(NULL, TMP_DIR, NULL, MS_PRIVATE | MS_REC, NULL));
 	clear_cap(_metadata, CAP_SYS_ADMIN);
 }

index e65e6cc80e22..21ed8afcc060 100644
@@ -216,14 +216,37 @@ static void mkdir_parents(struct __test_metadata *const _metadata,
 	free(walker);
 }
 
+static void
+maybe_warn_about_permission_on_cwd(struct __test_metadata *const _metadata,
+				   int err)
+{
+	char abspath_buf[255];
+
+	if (err == EACCES) {
+		const char *realp = realpath(".", abspath_buf);
+		if (realp == NULL) {
+			realp = ".";
+		}
+		TH_LOG("Hint: fs_tests requires permissions for uid %u on test directory %s and files under it (even when running as root).",
+		       getuid(), realp);
+		TH_LOG("      Try chmod a+rwX -R %s", realp);
+	}
+}
+
 static void create_directory(struct __test_metadata *const _metadata,
 			     const char *const path)
 {
 	mkdir_parents(_metadata, path);
 	ASSERT_EQ(0, mkdir(path, 0700))
 	{
+		int err = errno;
+
 		TH_LOG("Failed to create directory \"%s\": %s", path,
-		       strerror(errno));
+		       strerror(err));
+
+		if (strcmp(path, TMP_DIR) == 0) {
+			maybe_warn_about_permission_on_cwd(_metadata, err);
+		}
 	}
 }
 

@@ -1985,18 +2008,22 @@ TEST_F_FORK(layout1, relative_chroot_chdir)
 static void copy_file(struct __test_metadata *const _metadata,
 		      const char *const src_path, const char *const dst_path)
 {
-	int dst_fd, src_fd;
+	int dst_fd, src_fd, err;
 	struct stat statbuf;
 
 	dst_fd = open(dst_path, O_WRONLY | O_TRUNC | O_CLOEXEC);
 	ASSERT_LE(0, dst_fd)
 	{
-		TH_LOG("Failed to open \"%s\": %s", dst_path, strerror(errno));
+		err = errno;
+		TH_LOG("Failed to open \"%s\": %s", dst_path, strerror(err));
+		maybe_warn_about_permission_on_cwd(_metadata, err);
 	}
 	src_fd = open(src_path, O_RDONLY | O_CLOEXEC);
 	ASSERT_LE(0, src_fd)
 	{
-		TH_LOG("Failed to open \"%s\": %s", src_path, strerror(errno));
+		err = errno;
+		TH_LOG("Failed to open \"%s\": %s", src_path, strerror(err));
+		maybe_warn_about_permission_on_cwd(_metadata, err);
 	}
 	ASSERT_EQ(0, fstat(src_fd, &statbuf));
 	ASSERT_EQ(statbuf.st_size,

index 21ed8afcc060..e6891f59803a 100644
@@ -233,12 +233,41 @@ maybe_warn_about_permission_on_cwd(struct __test_metadata *const _metadata,
 	}
 }
 
+static int try_teardown_layout(struct __test_metadata *const _metadata)
+{
+	struct stat stat_buf;
+
+	if (stat(TMP_DIR, &stat_buf) < 0) {
+		return -1;
+	}
+
+	TH_LOG("Attempting to cleanup layout and retry...");
+
+	if (umount(TMP_DIR)) {
+		if (errno != EINVAL && errno != ENOENT) {
+			TH_LOG("Failed to unmount directory \"%s\": %s",
+			       TMP_DIR, strerror(errno));
+			return -1;
+		}
+	}
+	if (rmdir(TMP_DIR)) {
+		if (errno != ENOENT) {
+			TH_LOG("Failed to remove directory \"%s\": %s", TMP_DIR,
+			       strerror(errno));
+			return -1;
+		}
+	}
+	return 0;
+}
+
 static void create_directory(struct __test_metadata *const _metadata,
 			     const char *const path)
 {
+	bool retried = false;
+
+retry:
 	mkdir_parents(_metadata, path);
-	ASSERT_EQ(0, mkdir(path, 0700))
-	{
+	if (mkdir(path, 0700)) {
 		int err = errno;
 
 		TH_LOG("Failed to create directory \"%s\": %s", path,

@@ -246,7 +275,14 @@ static void create_directory(struct __test_metadata *const _metadata,
 
 		if (strcmp(path, TMP_DIR) == 0) {
 			maybe_warn_about_permission_on_cwd(_metadata, err);
+			if (!retried && errno == EEXIST &&
+			    !try_teardown_layout(_metadata)) {
+				retried = true;
+				goto retry;
+			}
 		}
+
+		ASSERT_TRUE(false);
 	}
 }
 

@@ -320,13 +356,15 @@ static void prepare_layout_opt(struct __test_metadata *const _metadata,
 {
 	disable_caps(_metadata);
 	umask(0077);
+
+	/* create_directory may try umounting then rmdir if tmp already mounted */
+	set_cap(_metadata, CAP_SYS_ADMIN);
 	create_directory(_metadata, TMP_DIR);
 
 	/*
 	 * Do not pollute the rest of the system: creates a private mount point
 	 * for tests relying on pivot_root(2) and move_mount(2).
 	 */
-	set_cap(_metadata, CAP_SYS_ADMIN);
 	ASSERT_EQ(0, unshare(CLONE_NEWNS | CLONE_NEWCGROUP))
 	{
 		TH_LOG("Failed to create new mount namespace: %s",